Chemical-reduction process by means of sodium amalgam



Sept. 15, 1925. 1,553,473

' G. POMA ET AL CHEMICAL REDUCTION PROCESS BY MEANS OF SODIUM AMALGAM Filed Aug. 3, 1921 2 Shun-Shut 1 121/ clztwls G .IPOIILQ/ i'btgs Sept. 15. 1925.

s. POMA ET AL CHEMICAL REDUCTION PROCESS BY MEANS OF SODIUM AMALGAM ,2 shim-sum 2 Filed Aug. 5, 1921 A ww- Patented Sept. 15, 1925.

UNITED STATES G'UALTIERO POMA AND GIUSEPPE PELLEGRINI, 0F MILAN, ITALY.

CHEMICAL-REDUCTION ZE'ROCESS Application filed August 1 '0 all whom it may concern:

Be it known that we, GUALTIERO POMA and GIUsErPE PELLEGRINI, subjects of the King of Italy, residing at Gesano Maderno, Milan, Italy, have invented certain new and useful Improvements in Chemical-Reduction Processes by Means of Sodium Amalgam, of which the following is a specification.

It is well known that among the various processes or methods of industrial manufacture of caustic alkalis a large importance attaches to the electrochemical ones. Electrochemical processes may be split into two classes according as they use a single electrolytic chamber with mercury cathode or two separate chambersan anodic and a cathodic one-separated by a porous diaphragm.

. To the first class belongs the Kellner-Solvay process (German Pat. N. 100.560 of 1898) which is the most largely used in the whole class. This process is characterized by the fact that the aqueous solution of the alkaline chloride undergoing electrolysis is made to flow between a movable mercury cathode and an anode consisting of a series of graphite cylinders. The mercury used as a cathode flows on the slightly inclined bottom of the cell and after having got charged with the alkaline metal that has become free through electrolysis, passes into a second cell where the amalgam comes into contact with water and is decomposed, giving rise to caustic alkali and free hydrogen. The movement of the mercury and therewith the continuity of the process are secured by means of a special circular elevator. Under these conditions the mercury amalgam shows an alkaline metal percentage which generally does not exceed 0.2%- and the aqueous solution of the caustic alkali produced shows a degree of concentration ranging from to The object of the present invention, for which protection within the meaning of the patent law is claimed, is the industrial employment of the alkaline amalgam such as isobtained in the'industrial manufacture of caustic alkalis as a means for reducing organic and inorganic compound substances.

The annexed drawing shows by way of example two methods of carrying the process into practice.

BY MEANS OF SODIUM AMALGAM.

3, 1921. Serial No. 489,592.

Fig. 1 is a diagrammatic view of a first form of apparatus that has been designed for the purpose and comprises a stirring device revolving about an horizontal axis.

Fig. 2 is a vertical center section of a second form of apparatus, in which the shaft is vertical instead of horizontal and has its bottom fitted with a pulley and with suspension and driving gears adapted to impart a rapid revolving motion.

Fig. 3 is an horizontal section through ww in Fig. 1. 4

I With reference to Fig. 1, 1--isthe electrolytic cell proper in which the salt solution undergoing electrolysis is circulated; 2 is the cell where as a rule the amalgam decomposes itself in the presence of water, giving rise to a solution of caustic alkali. The two combined cells 1 and 2 make up the Kellner-Solvay apparatus, -3., instead, represents the cylindrical reaction apparatus into which the mercury amalgam leaving the cell 1- is made to enter, thus shutting out, at least partly, the cell 2. By means of the elevator 4- the mercury leaving 3 is again brought into circulation in the Kellner-Solvay apparatus.

The reaction cylinder 3 is provided in well known manner with a very efficient stirring device, with a double wall whose intermediate space 5. permits of cooling down the system or also of heating it according as may be required, with various apertures for introducing a thermometer and the various reacting substances and for extracting samples, and finally with various mercury,

* water etc. seals.

With reference to Figs. 2 and 3 showing, as already said, a, second form of the apparatus the revolving shaft 6- has platforms or discs -7 keyed to it, the discs being made of any convenient material and fittedwith concentric projections or teeth 8.

Opposite the said discs are arranged as many discs -9 mounted on the elements -10 that make up the apparatus body or casing, the discs '9 bemg likewise provided with concentric projections or teeth 9' coming in between the teeth '8- of the discs -7'-. .6- is the pulley driving the shaft -6..-

Between one pair, of discs 79 and the next pair chambers. 11-, triangular in section, are provided for circulating the steam or the hot and cold water.

The working of the apparatus is as follows: 1

The alkaline amalgam and the substance to be reduced, which is held in suspension in water or other solvent, are introduced into the container built up of the elements 10--. throu h the holes -12- of the cover 13-'- an drop along the funnel-shaped incline14- and through the annular center opening -15+ on to the disc -8-- which, owing to its quick rotating motion,

- obliges them to flow by centrifugal force ing liquor is free from the alkaline metal,

. the mercu along with the. aqueous, alcohol acetonlc etc. liquids discharges itself through the holes -18; the mercury separates itself from the rest owing to its great-- er specific weight and is conveyed to the electrolytic tank by an ordinary elevator.

It will be understood that the apparatus shown may undergo considerable alterations in practice according as they must serve for instance to atonnze the mercury amalgam inthe aqueous solutions that must be reduced, and it is not excluded that, in

I order to obtain an intimate contact between the amalgam, andthe aqueous, alcoholic etc. suspensions, apparatus ma be used "that work as multiple centrifuga pum s etc.

Some examples of reductions o tained' by means of the process in questionwill illustrate the manner. in. which it may be carried lnto effect" and its practical importance.

1st Example-Preparation of hydrazobenzol from nitrobemzol.

- In to th apparatus are filled 200 litres of 10% solution of'caustic soda and .20 kilos nitroben'zol, the amalgam is then passed into the apparatus and the stirring device started. -It will soon beobserved that the 'mercury under the energetic action of the stirring device, though dividin itself into very minute drops inside of t e apparatus,

unites again into a solid mass as soon as it gets out of reach of the stirrer, the mass thenflowing through. the electrolytic cell, pipes, valves and liquid seals in a perfectly regular manner.

' During the first hours from the commencement of the reaction the temperature rises rapidly and can be maintained at abt.

60 C. onl by means of cooling; no giving off ofhy ogen is observed. Further on,

the activity of the reaction abates, so that heating through steam is required in order to keep the temperature between 60 and C. When the liquor is entirely discoloure'd, the reaction is completed; the hydrazobenzol. that has formed is then rapidly filtered and washed. If it is desired to con vert hydrazobenzol into benzidine, it suf-= fices' to bring it into suspension in a strongly acid solution of hydrochloric acid, to keep the latter in ebullition for some time till complete solution and then to treat it with so-" dium sulphate. The precipitation ofbenzidine sulphate is thus obtained. The resulting efliciencies are quite satisfactory.

W'ewish to mention that from the filtration of hydrazobenzol a nearly pure solution of caustic soda is obtained, the amount thereof being proportional to the amount of metallic sodium employed. The said soda can be ordinarily used 1n a large number of cases for instance in the, manufacture ofv soap, sodium hypochlorite etc.

From the abovesaid it appears, that, contrary to the industrial practice that has.

In asimilar manner orthotoluidine, di-

anisidiiie etc. can be prepared starting from orthomt'rotoluol or orthonitroanisol resp.

2nd Ewample -Prepamiion of aniline.

The experimental conditions of the foregoing example are repeated, saving that along with nitrobenzol pure water is filled -into the apparatus. By means of a suitable device hydrochloric or sulphuric or some other acid'is filled into the apparatus, the amount thereof bein equivalent to the amount of metallic so ium contained in the amalgam; the solution should show a slightly ac d reaction or even be neutral. The temperature rise is so rapid that it must be moderated by cooling. Nitrobenzol is thus reduced to aniline in a quantitative manner. 1

In a. similar manner toluidines, xylidines, phenylene and toluylene diamines, naphthylamine, ammosulphonic compounds, aminoxy-aminoxy-sulphonics of aromatic hydrocarbons etc. can be prepared. Aldehyde and ketone' compound nitrocarbocylic acids etc. can be reduced.

The economical convenience of working to the present method in the cases mentioned should be examined case by. case.

Many tlmes instead of filling pure water and then hydrochloric or sulphuric acid into carbonic or sulphuric anhydride in order to neutralize the forming soda. In this manner the alkalinity or acidity'of the solution can be kept very low in correspondence to the degree of hydrolysis of the alkaline bicarbonates or bisulphites, and at the end of the reaction, along with the reduced substance, considerable quantities of carbonate, bicarbonate, sulphite or bisulphites may be obtained.

' The presence of bisulphite greatly assists in the reduction.

3rd EmampZe-Prpardtion of paranm'nm phenol In a vessel similar to the one already described but made of glazed cast iron 'or of an acidproof alloy or lined with a suitable enamel is filled an aqueous solution of sulphuric acid, along with nitrobenzol. The temperature is raised to and then kept at -80 C.

The weight proportions should be so adjusted as to again obtain a strongly acid solution at the end of the reduction.

The reduction takes place in a complete manner with formation of p-aminophenol sulphate and of small proportions of henzidine and aniline sulphate.

In a similar manner a number of photographic rev ealers can be obtained as well as of other products of industrial interest such as, for instance; diamidophenol, amidophenol carbocylic acids and their ethers, the amidophenols. of the quinoline series, the

ethers of the,amidophenol derived from al- 4thPrepamtz'on 02 sodium hydrosclphite and su phomylates.

The method above described may be used also for obtaining inorganic roducts.- For instance if in an apparatus li e the one described a stream of sulphuric acid is led in such a quantity that for each molecule of anhydricle therebe present two atoms of sodium, a solution of hydrosulphite is formed which, if conveniently cooled, does not decompose and can be pursued up to saturation.

If as solvent for the sulphuric anhydride water is used, alkaline hydrosulphites are obtained either in aqueous solution or solid with crystallization water; if instead suitable organic solvents are used such as benzol or alcohol etc. anhydrous hydrosulphites are obtained.

If along with the other components formic aldehyde or acetic aldehyde or acetone are introduced into the vessel, the corresponding sulphoxylatcs are obtained which, like hydrosulphites, meet the highest importance in the dyeing industry.

The chemical reduction process or method claimed in the present must be considered, in

its complex as intended, among other purposes, to replace the electrochemical reduction process, over which obvious advantages of technical. economical and practical character may be claimed for it. The novel method is perfectly successful even in those cases where, as for hydrosulphites, the electrochemical method has given no practical results whereas on the other hand the novel method as compared with the ordinary chemical reduction methods, presents all the advantages that, used to be considered as characteristic and exclusive merits of the electrochemical processes.

We claim:

1. The combination of a process of reduction with the electrolytic process for industrially producing a caustic alkali, which combination comprises the steps of continuously electrolyzing a solution of an alkali metal salt under normal conditions while in contact with a mercury cathode, whereby a mercury amalgam of the alkali metal is formed, continuously bringing such amalgam into intimate contact both with water in order to obtain the caustic alkali and with an oxygen-containing organic compound capable of being reduced, and continuously carrying back the mercury to the electrolytic cell.

The combination of a process of reduction with the electrolytic process 'for industrially producing a caustic alkali, which combination comprises the steps of continuously electrolyzin'g a solution of an alkali metal salt under-normal conditions while in contact with .a mercury cathode, whereby a mercury amalgam is formed, continuously bringing such amalgam into intlmate contact both with water in order to obtain the caustic alkali, and with a reducible nitrogencontaining organic compound capable of being reduced, and continuously carrying back the mercury to the electrolytic cell.

4:. The combination of a process of reductionwith the electrolytic process for industrially producing a caustic alkali, which combination comprises the steps of continuously electrolyzing a solution of an alkali metal salt under normal conditions while in contact with a mercury cathode, whereby a mercury amalgam is formed, continuously ibringing such amalgam into intimate contact both with water in order to obtain the caustic alkali, and with an inorganic substance which is diflicultly reducible, and continuously carrying back' the mercury to the electrolytic cell.

5. The combination of a process of reduc, tion with the electrolytic process for industrially producing acaustic alkali, which combination comprises the steps of continuously electrolyzing a solution of an alkali metal salt under normal condition, while in contact with a mercury cathode, whereby a -mercury amalgam of the alkali metal is' suchamal- -with water GUALTIERO POMA. GIUSEPPE PELLEGRIN 1. 

